TS9201: Invalid Macro Argument Count

Category: Macro Syntax
Severity: Error

Message

'{macro}' expects {expected} argument(s), got {actual}

Explanation

This macro was called with the wrong number of arguments. Each macro has a specific signature that must be followed.

Common Examples

summon() - Too few/many type arguments

// Error: summon() expects 1 type argument
summon(); // TS9201
summon<Eq, Ord>(); // TS9201

// Correct:
summon<Eq<number>>();

comptime() - Missing callback

// Error: comptime() expects 1 argument
const x = comptime(); // TS9201

// Correct:
const x = comptime(() => 1 + 2);

@derive() - Empty arguments

// Error: @derive() expects at least 1 argument
@derive() // TS9201
class Point {}

// Correct:
@derive(Eq, Clone, Debug)
class Point {}

How to Fix

1. Check the macro documentation for the correct signature
2. Ensure all required arguments are provided
3. Remove any extra arguments

Macro Signatures Quick Reference

Macro	Signature
summon	summon<TC<T>>()
comptime	comptime(() => expr)
@derive	@derive(TC1, TC2, ...)
@instance	@instance (no args)
implicit	= implicit() (no args)
specialize	specialize(fn)
pipe	pipe(value, fn1, fn2, ...)

See Also

• TS9202 - Invalid macro argument type
• Macro Reference